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May 12, 1959 N. c. wwTwER, JR 2, 7

ELECTRODE SUPPORT AND SFACING STRUCTURE FOR ELECTRON DISCHARGE DEVICES 2 ShuthShut 1 Filed 001.. 9. 1956 FIG! ATTORNEY May 12, 1959 N. c. WITI'WER JR 2,886,7 4

ELECTRODE SUPPORT AND smcnic STRUCTURE FOR ELECTRON mscnmcs: navzcxss 2 Shasta-Shoat 2 Fild Oct. 9. 1955 FIG. 3

IN I/EN TOR N. c. w/rrwm, JR.

mcmm ATTORNEY United States Patent Ofifice ELECTRODE SUPPORT AND SPACING STRUC- TURE FOR ELECTRON DISCHARGE DEVICES Norman C. Wittwer, Jr, Oldwick, NJ, assignor to Bell Telephone Laboratories, Incorporated, New York, N.Y., a corporation of New York Application October 9, 1956, Serial No. 614,837

9 Claims. (Cl. BIS-27! This invention relates to electron discharge devices, and more particularly to electrode assemblies for electron discharge devices.

In planar electrode devices having interelectrode spacings of the order of 0.001 inch, the problem of attaining the desired spacings is a diificult one. Another asacult problem, the desired spacings having been attained, is that or preventing permanent distortion of the electrodes when the assembly of which they are a part is subjected to shock, physical impact, severe vibration, or temperature change.

With a control grid to cathode spacingin an electron discharge device of the magnitude oi 0.001 inch, a change in the spacing or a variation in the spacings of dlfiereut areas of the electrodes of only 0.0001 inch may cause a pronounced change in the transconduotance of the device and a consequent failure to meet the requisite performance characteristics.

To minimize interelectrode spacing changes due to permanent distortion resulting from shock, impact, and vibration, the electrodes must be as rugged and stable as possible. However, it. is not practicable to mount the electrodes in an absolutely rigid support structure because of the tendency of the electrodes to expand when heated. Rigid mounting and thermal expansion could combine to cause buckling and bowing of the cathode and, as a result, spacing changes and variations. Thus, while a planar electrode mounting structure must provide secure electrode support, it must also, in many applications, allow for longitudinal shifting of the cathode in response to temperature changes.

An object of this invention is to improve the electrode mounting structures of electron discharge devices.

More specifically, an object of the present invention is to maintain accuratelydetermined electrode spacings during the entire life of an electron discharge device.

A further object of this invention is to allow substantially unrestricted expansion and contraction oi a planar electrode in an electron discharge device, thereby maintaining accurately the spacing between it and other electrodes.

Another object of the present invention is an electrode supporting structure which is sturdy and readily assembled These and other objects are attained in one specific illustrative embodiment of this invention wherein in an electron discharge device the spacing between a planar cathode and a control grid is accurately maintained. The ends of the cathode and of the control grid assembly are supported by flexible mica discs which are positioned in planes perpendicular to the main axis of the electrodes. An electrode receiving opening in each mica member forms a straight line reference surface against which the,

7 spring members, one at each cathode end.- A wire spring extends between each cathode end and its associated mica member, each spring being anchored to a cathode end by a strap element and hooked through a mica member aperrare.

The flexible mica labs are designed to impose minimum constraints and therefore minimum distorting forces on the cathode as it moves in response to changes in temperature; that is, it a mica reference surface is fixed with respect to its position on the cathode surface which it contacts, the flexible mica tab or hinge, rather than the cathode, will be temporarily distorted or bent as the combined result of sticking action and the cathode movement. I

The use of wire spring members in combination with flexible mica tabs in an electron discharge device of the type more specifically described hereinbelow efiectively provides desired cathode loading while imposing a minimum of constraints on cathode movement. Thus, buckling and bowing of the cathode and permanent changes in the cathode-control grid spacing are minimized. Furthermore, the spring members, while freely allowing cathode movement due to thermal elfecls, make unnecessary any additional provision for preventing excessive longitudinal movement or walking of the cathode.

Accordingly, a feature of the present invention is a planar cathode resiliently biased against mica member reference surfaces by wire spring members connected between the cathode ends and the micas.

A further feature of this invention resides in the provision of relief slots in the mica members for the purpose of attaining flexible mica tab supporting elements.

Another feature of the present invention is the cooperation between the wire springs and the flexible mica tabs to impose minimum constraints on a cathode moved by I beat eiiects, thereby reducing cathode bowing and buckling to a point where the cathode-control grid spacing remains substantially constant over a wide range of operating temperatures. At the same time the non-- rigid mica tab-wire spring mounting and longitudinal positioning structure is rugged enough to withstand severe shock, physical impact and vibration.

A complete understanding of this invention and oithe various features thereof may be gained from considerstion of the following detailed description and the accom-- trode assembly illustrative of the principles of the present invention which may be easily arranged and mounted in p any one of a great variety of devices by anyone skilled in the art of electron discharge devices.

A left-hand insulator assembly 10 and a right-hand insulator assembly 11, both of which are advantageously of flexible mica, contain electrode receiving openings 12 .therethrough, the mica edges 13, 14 and 15 of which are relente May 12, rsssl.

in a straight line and form a part of the reference surface against which a cathode l6 and the support rods 17 of a control grid are biased r loaded. The mica assemblies 10 and 11 contain relief slots 18 so located as to form mica tabs or hinges 20, the free ends of which are in contact with the electron emissive side 21 of the cathode 16.

Also shown in Fig. l are an anode elem nt 22, an anode support rod 23, assembly support rods 25. control grid cross memb r s 47 and coil spring supporting member 28. The member 28. advantageously welded to the assembly support rods 25, supports a spring whose Cmls exert a force on a heat shield 33. The heat shield, in turn, bears against the c ntrol grid support rods 17 and loads them against the reference surfaces 13 and in the mica discs 10 and ii. The ends of the anode support r d 23 and of the assembly support rods 25 have eyelets 24 attached thereto as a means of securing the rods 23 and 25 to the disc members 10 and 11.

The cathode 16, advantageously a Hat, hollow member having any suitable electron emissive material coated thereon, is positioned between the control grid support rods 17 and adjacent a plurality of lateral wires, not shown in Fig. 1, secured to the rods 17 to form a grid structure. The cathode 16 is biased against the mica reference surfaces by means of wire spring elements 31 and 32.

Referring nor: to Fig. 2, there is clearly shown the cathode 16 of the electrode assembly of Fig. l. One end of the wire spring element 31 is hooked through an aperture 33 in the right-hand mica disc 11, the other spring end being anchored to the cathode 16 by a strap 34 which is advantageously welded to the right-hand end of the cathode. The second spring element 32 is similarly connectcd between a strap secured to the left-hand cathode end and an aperture 35 in the left-hand mica assembly 10. The springs 31 and 32 maintain the cathode 16 in intimate contact with the reference surfaces of the mica assemblies and also prevent excessive longitudinal movement or "walking of the cathode.

A: seen in Fig. l, the portions of the grid support rods 17 which rest in contact with the straight line reference surfaces of the micas are stepped. Since the lateral grid wire. 40, shown only in Fig. 3, are wound over unstepped portions of the grid rods, it is clear that the difference between the grid rod dimensions x and y, indicated in Fig. 3, determines the spacing between the emitting surface of the cathode and the lower surface defined by the lateral wires 40. The depth of the stepped portions, and thus the cathode-control grid spacing, can, of course, be very accurately determined in, for exam le, a grinding operation. For a more detailed description of this type of spacing means, reference may be made to Patent 2,663,819, C. T. Goodard, December 22, 1953.

The illustrated electrode assembly, while being mechanically rug .d and stable, exhibits sufficient flexibility to maintain the critical cathode-control grid spacing virtually constant over a wide range of temperatures. Any sticking that occurs between the mica supporting surfaces and the contacted cathode portions during cathode movement results in movement or swinging of the mica tabs; thus, provision is made for substantially free thermal expansion and contraction of the cathode in a direction perpendicular to the mica assemblies ,0 that buckling and boving and electrode spacing changes caused thereby are eliminated.

It is to be understood that the above-described embodiment and arrangement is merely illustrative of the application of the principles of the present invention. Numerous other arrangements may be made by those skilled in the art without departing from the spirit and scope of this invention.

What is claimed is:

l. An electron discharge device comprising a cathode having a fiat surface, an electrode having a plurality of wires adjacent said cathode, means defining reference planes for said cathode surface and for said electrode wires, flexible insulat ng tongue members perpendicular to the main axis of said cathode and having straight edges in said cathode surface reference plane contiguous said cathode surface, and wire springs, each wire spring con nccting said cathode and a tongue member and biasing said cathode against said tongue member, whereby said cathode is positioned in said cathode surface reference plane and, within preassigncd limits. the longitudinal movement of said cathode due to heating effects is substantially unrestricted.

2. An electron discharge device comprising a first elc trodc surface, a second electrode 5t1rf"cc, means defining reference planes for said electrode surfaces, flexible insulating tongue members having straight edges in said first electrode surface reference plane and contiguous said first electrode surface, and wire springs, each wire spring connecting said first electrode surface and a tongue memher and biasing said first electrode surface against said tongue members.

3. An electrode assembly for electron discharge devices comprising a cathode having a planar emitting surface, a control-grid surface adjacent said cathode, means defining reference planes for said emitting surface and said control-grid surface, flexible insulating tabs perpendicular to the main axis of said cathode and having Straight edges in said emitting surface reference plane contiguous said emitting surface, and spring members, each spring mem ber connecting said cathode and an insulating tab and biasing said cathode against said insulating tab.

4. An electron discharge device comprising a cathode surface, a eontrol-grid surface. means for maintaining an accurately'detcrmined spacing thcrebctween, Enid main taining means including flex ble insulating tabs in contact with said cathode surface, and spring members, each spring member being connected between said cathode surface and one of said tabs.

5. A11 electrode assembly for electron discharge devices comprising a first and a second electrode surface, means for maintaining an accurately-determined spacing tberebetween, said maintaining means including flexible mica tabs having straight line reference surfaces contacting portions of said first electrode surface and wire spring members connecting said first electrode surface and said mica tabs.

6. An electrode assembly comprising a plurality of flexible insulating tabs, electrode means in contact with said insulating tabs, and means biasing said electrode means against said insulating tabs including spring memberg cgngegting cm'd electrode means to said insulating tabs.

7. An electrode assembly for electron discharge devices comprising an emitting surface, a control electrode surface, means for attaining a desired spacing between said surfaces including flexible mica tabs in contact with said emitting surface, and spring biasing means connected between said emitting surface and said mica tabs.

3. An electrode supporting structure comprising :1 p1,: rality of mica assembly members having electrode receiving openings and relief slots thcrethrough. mica edges of said openings forming straight line reference surfaces, said openings and slots forming mica tongues, a cathode hav ing a flat surface, a control grid, and biasing means con nectt N68 said cathode and said mica tongues, whereby said cathode is resiliently biased against said reference surfaces and its spacing with respect to Stltl cont ol grid is accurately maintained, the biasing means also limiting the longitudinal movement of said cathode wilhin a prcassigned range.

9. An electrode assembly comprising a planar cathode. a planar grid, spaced iusult'lting supports for the cathode and the grid, means for maintaining coniigumh l'nt'cs oi said cathode and grid in pro tr relation. said nzcmu in cluding a flexible tongue portion of each of and supports. said tongues each having an end edge in contact with the grid contiguous face of the cathode, spring means con neeted between spaced portions of the cathode and the respective supports for biasing the cathode toward said tongues, each snppolt having edge portions in line with the end edges of saidtongues, the edge portions and end edges defining a reference plane, and grid support means bearing on said edge portions to maintain the cathode contiguous face of the grid in spaced parallel relation to the cathode.

References Cited in the file of this patent UNITED STATES PATENTS Ackman July 21, 1936 Alma Ian. 17, 1950 Walsh Oct. 24, 1950 Zorgman Nov. 4, 1952 Goddard Dec.'22, 1953 Piles Ian. 22, 1957 

